This is an ACTG sponsored multicenter, non-randomized efficacy trial of oral AZT at a dose of 180 mg/kg q6h in children 6 months to 12 years of age with AIDS or with other serious manifestations of HIV infection. Efficacy will be determined by comparing the course of infection in treated children with the course of a carefully chosen cohort of historical controls from the same institutions. Participants are followed for one year for evidence of AZT toxicity, for clinical and virologic evidence of progression of HIV infection.